How fast was the Cray?

Cray-1 – the eight million dollar super-computer

By Frederic Friedel

As a young TV science journalist at the beginning of the 1980s I travelled to the Max Planck Institute for Astrophysics in Garching, near Munich, Germany. They had the fastest computer in the world, a Cray-1, and I was there to do a story about it. I remember entering Max Planck with my film crew, sitting down and telling some scientists why we had come. Then I asked “where is the computer, the Cray?” – “You are sitting on it,” they replied. Oops, right they were. This is what the Cray-1 looked like:

The Max Planck Cray-1, with storage units in the background. Each could hold three gigabyte!

Of course when you took off the panels of the tower and the base things looked different

This super-computer had been developed by CDC engineer Seymour Cray, who had found backers on Wall Street for the project. It took four years to build, and in 1975 when the first 80 MHz Cray-1 was announced, interest was so high that a bidding war broke out between the Lawrence Livermore and the Los Alamos National Laboratories. The latter eventually won and took delivery of a trial machine with the serial number 001. The first regular customer was the National Center for Atmospheric Research (NCAR). They payed $8 million for a Cray-1 (serial number 3) and a million for storage disks. Over the years Cray Research sold over eighty Cray-1s, making it one of the most successful supercomputers in history. You will find a lot more information on this at Wiki.

Anyway, I was absolutely thrilled to see the Max Planck super-machine, and my six-minute piece on it for German TV was positively effusive. A couple of years later I got to see another Cray, this one in the basement of the Bell Laboratories, where my friend Ken Thompson had access to it. It was faster and more advanced than the one in Germany, and we dutifully drooled over it.

Robert Hyatt and Albert Gower (on the right) who have defeated Ken Thompson
and Joe Condon (left) who held the title with their dedicated Belle machine

Around 1980 Cray Research chose to sponsor the program "Blitz", written by Robert Hyatt, Harry L. Nelson and Albert Gower. It was ported to the Cray and participated in computer chess events until the mid 1990s. "Cray Blitz" won several ACM computer chess events, and two consecutive World Computer Chess Championships, the first in 1983 in New York City, and the second in 1986 in Cologne, Germany.

Cray Blitz and the wrong bishop

Recently I wrote an article on an endgame involving a “wrong bishop”. For those of you who missed it here is a summary. The endgame king, bishop and pawn vs king is always a draw when

1. the pawn is on the a or h-file and the bishop does not control the promotion square;
2. the defending king can reach the promotion square in time to defend it.

For a long time this simple piece of chess knowledge eluded chess playing computers. They simply couldn't calculate all the way to the promotion, and without specific instructions on how to handle the position they would often take a wrong decision. During the 1980s, when the first programs were being told about the wrong bishop draw, I devised a test position to find out if they could handle the endgame correctly.

The temptation for early day computers was simply too great. They went astray for the following reasons:

1. a bishop is valued higher than a knight, especially in open endgame positions;
2. Kxe5 centralises the king, while Kxc5 doesn't
3. if it takes the knight the black pawn advances all the way to h2, where it gets a lot of bonus points for being one square away from promotion. After taking the bishop it can be kept on the top half of the board.

So any sensible computer would take the bishop, unless of course it was told to do otherwise. Which seemed to be the case in the following game.

At the time this was celebrated as the first instance of practical chess knowledge, implemented into a computer (the “intelligent method”), leading to a victory when otherwise a draw would be expected. But some time later I obtained the computer logs and discussed the position with Harry Nelson of the Cray team. It turned out that Cray Blitz had simply searched deep enough to see the promotion after 4...Be4, – by pure brute force –, while it found no queen on the board after 4...bxa5. It was that simple.

In part two of my article I told you how I had shown a subtle wrong bishop position to strong grandmasters, including former World Champions Mikhail Botvinnik and Mikhail Tal – and to the Computer Chess World Champion Cray Blitz. It spent 13 seconds considering a wrong key move – with a logical +4.032 score. Then, at ten ply, it switched to the correct move and displayed +10.878. Mikhail Botvinnik saw this all happen and he was not at all happy that a computer was able solve the position so effectively by pure brute force, without the chess knowledge he, a proponent of the "intelligent method", so ardently advocated.

How fast was the Cray-1?

While I was writing these historical articles I started to wonder: how fast, exactly, was the Cray-1 , and how did it compare to today’s machines. It was expedient that our friend John Nunn had just bought his son Michael a good mid-range graphics card for his 18th birthday. John did some calculations for me and wrote back: “The Cray-1 could do 130 Megaflops" [million floating point operations per second]. "The NVidia Graphics card in Michael’s computer can do 2258 Gigaflops. So it is about 17,000 times as powerful by this measure.” John conceded that, of course, the architectures are very different.

Seventeen thousand times more powerful? A card you can hold in the palm of your hand, and which costs around $300?

I consulted Ken Thompson on this – he has been work on the forefront of computing for over fifty years. Ken, who never capitalizes anything, wrote:

the cray had 2–5ns cycle time. (depending on model) in that time, it could get up to 7 arithmetic units executing an instruction. the vector length was 64 and it took a few instructions to start and a few to shut down. some models had up to 8 processors. so, peak rate is about 0.5G (2ns) * 7 * 8 or about 25G. now to get to reality – not everything can be vectored. and when you can vector, usually only a few of the units are used. in fact, most instruction are simply run at the clock rate. some instructions take multiple units (divide, square root). but the cray had huge bandwidth to memory. the i/o was staggering.

You figure this out. Do you believe that the factor 17,000x is possible, or are we making a logical mistake? Experts, please tell us in our feedback section below.

Source: Frederic Friedel at Medium.com